The molluscs have the widest variety of eye

Eye

Eyes are organs that detect light and convert it into electro-chemical impulses in neurons. The simplest photoreceptors in conscious vision connect light to movement...

 morphologies of any phylum

Phylum

In biology, a phylum The term was coined by Georges Cuvier from Greek φῦλον phylon, "race, stock," related to φυλή phyle, "tribe, clan." is a taxonomic rank below kingdom and above class. "Phylum" is equivalent to the botanical term division....

, and a large degree of variation in their function. Cephalopods' eyes are as complex as those of vertebrates; scallop

Scallop

A scallop is a marine bivalve mollusk of the family Pectinidae. Scallops are a cosmopolitan family, found in all of the world's oceans. Many scallops are highly prized as a food source...

s have up to 100 simple eyes; and some bivalves have compound eyes.

Diversity

Eyes have evolved independently between seven and eleven times in the molluscs, which goes some way to explain the diversity of eye types observed. Molluscs have eyes of all levels of complexity, from the pit eyes of many gastropods, to the pinhole eyes of the Nautilus

Nautilus

Nautilus is the common name of marine creatures of cephalopod family Nautilidae, the sole extant family of the superfamily Nautilaceae and of its smaller but near equal suborder, Nautilina. It comprises six living species in two genera, the type of which is the genus Nautilus...

, to the lensed eyes of the cephalopod

Cephalopod

A cephalopod is any member of the molluscan class Cephalopoda . These exclusively marine animals are characterized by bilateral body symmetry, a prominent head, and a set of arms or tentacles modified from the primitive molluscan foot...

s. Compound eyes are present in some bivalves, and reflective 'mirrors' have been innovated by other lineages.such as scallop

Scallop

A scallop is a marine bivalve mollusk of the family Pectinidae. Scallops are a cosmopolitan family, found in all of the world's oceans. Many scallops are highly prized as a food source...

s. As well as complexity, the eyes of molluscs span a huge range in size; they may be from 20 µm to 27 cm across.

Anatomy

Gastropods and cephalopods have paired eyes on their heads (and sometimes tails), but many molluscs do not have clear head regions in which to locate the eyes. Consequently, many molluscs may have a multitude of eyes in more unlikely places, such as along the edge of their shell. Chitons have a dispersed network of tiny eyes

Aesthete (chiton)

Aesthetes are visual organs in chitons. They are tiny 'eyes', too small to be seen unaided, embedded in the organism's shell. They may act in unison to function as a large, dispersed, compound eye. They are light sensing organs that are derived from the mantle of the organism.Some chitons also...

 over the surface of their shells which may act together as a compound eye.
Many gastropods have stalked eyes; the eye can be retracted into the stalk itself in the presence of danger.

See also

• Arthropod eye
  Arthropod eye
  The arthropods ancestrally possessed compound eyes, but the type and origin of this eye varies between groups, and some taxa have secondarily developed simple eyes...
  
  
• Parietal eye
  Parietal eye
  A parietal eye, also known as a parietal organ or third-eye or pineal eye, is a part of the epithalamus present in some animal species...
  
  
• Sensory organs of gastropods
  Sensory organs of gastropods
  Sensory organs of gastropods include olfactory organs, eyes, statocysts and mechanoreceptors. Gastropods have no sense of hearing.- Olfactory organs :...
  
  
• Simple eye in invertebrates
• Vision in fish